Susan Maingi, Jackline Ndiiri, Bancy Mati



Estimation of Crop Water Requirements for Garden Pea, Sweet Pepper and Tomato using the CropWAT Model in Maragua Watershed, Murang’a County, Kenya

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Kenya is a water scarce country and its water resources are limited. It is therefore significant to wisely utilize the little available water whether in agriculture or any other use. Agriculture being one of the key areas where water is a key input for growth, determination of crop water requirement is one of the key considerations for accurate scheduling of irrigation especially during the dry season when rains subside. This study was carried out to determine the crop water requirements and irrigation scheduling of garden peas, sweet pepper and tomatoes for the Kambirwa, Gituamba and Maragua ridge regions of Maragua watershed located in the Upper Tana Catchment. The crop water requirement for each of the crops was determined by FAO CROPWAT 8.0 model which is developed by the Food and Agricultural Organization (FAO), using 10 years climatic data which was obtained from Upper Tana meteorological station. The model is a computer based programme for the calculation of crop water and irrigation requirements from existing or new climatic and crop data. To determine the crop water requirements (CWR), reference crop evapotranspiration (ETo) and crop factor (Kc) were used. The reference crop evapotranspiration (ETo) was determined using meteorological data. The metrological parameters used are Maximum Temperature, Minimum Temperature, Wind Speed, Relative Humidity and Sunshine Hours and are considered as input and Reference Crop Evapotranspiration is considered as output. The study results showed that ET0 varied from 3.01 to 5.10 mm/day and the effective rainfall varied from 8.0 to 154.4 mm. The crop water requirements for Garden pea, sweet pepper and tomato are 395.6, 460.1 and 432.7 mm/dec respectively. The irrigation requirements were 155, 187.7 and 158.7 mm/dec for garden pea, tomato, and sweet pepper respectively. The total gross irrigation mean and the total net irrigation mean are 190.9 mm and 133.7 for garden pea with two irrigation schedules,116.1 mm and 81.3 mm for tomato with six irrigation schedules and 67.2 mm and 47.0 mm for sweet pepper with six irrigation schedules. This study has proved that the CropWAT model is useful for calculating the crop irrigation needs which will help in proper management of water resources.


CropWAT; Irrigation schedules; Irrigation requirement; Crop water requirement


Cite this paper

Susan Maingi, Jackline Ndiiri, Bancy Mati. (2020) Estimation of Crop Water Requirements for Garden Pea, Sweet Pepper and Tomato using the CropWAT Model in Maragua Watershed, Murang’a County, Kenya. International Journal of Agricultural Science, 5, 112-123


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